Constant-voltage system.



T. SPENCER CONSTANT VOLTAGE SYSTEM.

APPLICATION FILED JUNE-H, 1914.

1,220,371" Patented Mar.27,1917.

1TB. E

ITNESSEIIS- IN VENTOR,

' TH P N H -W B MAS 5 CE 2 v y Q W ATTORNEY U IT D STATES PATENT OFFICE.

TiIOMAS sPENoER, 0E PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO HELIOS MANU- FAo'rUItING COMPANY, A CORPORATION OF PENNSYLVANIA.

GONSTANTWoL'rAGE SYSTEM.

Specification at Letters Patent.

. Patented Mar. 27, 1917.

Application filedlnne 11, 1914. Serial No. 844,550;

To all whom it may concern:

Be it known that I, THOMAS SPENCER, a citizen of the- United States, residing at Philadelphia, in the county of Philadelphia. and State of Pennsylvania, have invented a certain new and useful Improvement in Constant-Voltage Systems, of which the following is a full, clear, and exact description.

Generally speaking, my invention consists in employing opposing fields, one having values in accordance with Frolichs equation and it is the object of my invention to accomplish this result.

In the drawings:

Figure 1 is a conventional illustration of a constant voltage system in accordance with my invention.

Fig. 2 is a modification.

The main armature 1 of the generatoris rotated in the adjacent fields 2 and 3 by some source of power, such as a car axle for instance. Current for the windings 4: and 5 respectively of these fields is supplied from a constant voltage system such as a storage battery 6. An exciter armature 7 is mounted on the same shaft as the main armature, or it may be mechanically connected thereto to rotate at a proportional speed. The field 8 of. the exciter has a winding 9, also magnetized by current from the storage battery and in the drawing these windings are shown connected in series, but it will be evident to one skilled in the art that the same result could also be obtained by connecting the fields in parallel, by properly proportioning the field resistance or the voltage of the battery. Upon field magnet 3 is wound a secondwinding 10 which is connected with the terminals of the exciter 7 The direction of the magnetizing force of the winding 10 is opposite to that of winding 5, and a resultant field is obtained which varies with the speed of rotation of theprime mover. The commutator 11 of the main armature 1 may have its brushes directly connected with the terminals of the lighting or other load 12 throu h the usual automatic cut-out switch 13. eversing switches 17 and 18 (Fig. 1) are inserted in the load circuit 12 and field circuit 10 respectively to reverse the direction of the current in these circuits when the direction of rotation of the prime mover is changed.

In practice, this switch may be combined with switch 13.

Fig. 2 illustrates a modified wiring arrangement requiring only one battery 15, and a single reversing switch 19. One terminal of coil 9 is connected permanently to the central points of the reversing switch and the other terminal to the storage battery, so that the direction of this field is always the same. lVhen the direction of rotation of the armature 7 is changed, the direction of the variable field 10 is therefore reversed and the reversing switch 19 simultaneously reverses the direction of the cur-- rent in the field coils 4: and 5. The value of the resultant field is therefore preserved, but the polarity reversed whenever the direction of rotation is reversed. The current taken from the commutator 11 is thus always in the same direction.

The manner in which either arrangement fulfils'the'constant voltage requirement will be understood from the following explanation:

It'has been shown by Frolich that within certain limits, a magnetization curve closely follows the law:

ilia where y is the flux, w the M. M. F. producing this flux and a and b are constants. This equation can be transposed into the following form, which is more convenient for this proof:

Now, in the arrangement given by way of example above, two fields 2 and 3 are used,

and the constant field 2 isso designed that it has a value a and I) having the value of the constants in equation (2) and field 3 is made with two \windings' 10 and 5 having opposing M; M. 'F.s m and 70 respectively; a varying directly with the speedbf the rotation of the armature shaft andt' being a constant of a value 5r of equation 2 Then the M. M. F, in

the equation is equalto and if this value issubstituted \for a: in

0 equation (2), field 3 would have a valuefof,

and since field 2 has a constant alue of so of opposite polarity to tha'totfield 3, then.

the resultant gfield acting.- on the armature would be the difierenq'e between the two differential fields? and 3 or,

Bearing in mind that the variable magneto Inotiveli'orce'm 1s made proportional to the --,"'"speed S, this expression reduces to The voltage developed in the generator of an armature follows the well known law E=KBS. V here K is a constant, B is the field strength and S the speed of rotation.- Then and by arranging a system in this way, G5 constant voltage may be therefore obtained direction.

% by a second field produced by the at allspeeds within which the magnetization curve closely resembles the curve For ordinary purposes the conditions are such thatthe previous result is closely obtained for all speeds between 20 and 80 miles per hour. Below and above these limits, th attery carries the load.

It will,- also ,be noted that whenever the direction of rotation of the armatures l and 7 is changed, the reversing switch 17 is operated to keep the resultant field in the same A 0 Hysteresis can have no appreciable efi'pct 8 on the operation as a metalcan be chosen which has negligible hysteretic properties. .An instance of such is the cast steel usually used infield cores for train lighting generators especially. Armature reaction can also beovercome in the same manner as in other systems by the use of appropriate inter-poles or by other ar- .4 ran ements. I 96 T e figures are merely conventional showings of the'way of carrying out the invention and the invention is not to be limited thereto. It will be understoodthat in prac tice, fields 2 and 3 may each consist of one or more pairs of poles, the number being immaterial as far as the invention is concerned. Having described my invention, what I claim is:

1. Themethod of generating a constant 100 voltage which consists in rotating armature conductors in a-resultant field produced by opposing. a constant field, of a value "of difference between, a variable M. M. F. m, proportional to the cutting speed of said conductors, and a second M. M. F. of the value %,said terms 6, 72 and 2:, having the no relation given in Frolichs equation m am y 1 5:0 2. In a constant voltage system, the combination with a rotatable main armature of a field pole having a coil, a second field pole having two'coils, a source of constant E. M. F. connected to energize the coil onthe first .field pole and one coil on thesecond field 12o changes.

10 energize the remaining field coil, and means Patent Oflice.

[SEAL] for reversing the current in the field coils included in the series circuit without reversing the current in said field winding.

In testimony whereof, I hereunto afiix my signature.

' THOMAS SPENCER.

\Vitnesses:

REED H. KLAN E, C. WV. GULDEN.

It is hereby certified that in Letters Patent No. 1,220, 37 1, grantedMarch 27 1917, upon the application of Thomas Spencer, of Philadelphia, Pennsylvania, for

an improvement in Constant-Voltage Systems, an BIIGI appears in the printed specification requiring correction as 'follows: Page 2, line -59, for the equation A, 13: KS read E KS; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Signed and sealed this 1st day of May, A. 1)., 1917.

R. WHITEHEAD,

Acting Commissioner of Patents. 

